Did Kerala and Uttarakhand receive relentless rains in October due to climate change?
The story so far: Even as the southwest monsoon began to recede from the subcontinent, Kerala and Uttarakhand received record rainfall in October. In these two states and others, in recent years there have been variations in the pattern and intensity of precipitation. Kerala had experienced a serious period in 2018, which took its toll. This year’s rain has also claimed lives in Kerala and Uttarakhand.
How much rain is there?
According to the Indian Meteorological Department (IMD), the Kerala and Mahe region received 124% excess rainfall from October 14 to 20. Against the normal rainfall of 72.1 mm for the period, the region had received 161.2 mm. Lakshadweep received 15% excess precipitation. From October 1 to 22, Kerala recorded 121% excessive rainfall, with all districts except Alappuzha recording more than 70% excessive rainfall. Alappuzha recorded 52% overrun over the period. The agency’s latest bimonthly forecast indicates that “above normal” precipitation is expected during the next fortnight. Uttarakhand recorded 192.6mm versus the usual 35.3mm from October 1 to 20, with several districts reporting 24-hour highs exceeding figures by more than a century.
What explains the torrential rain?
There are different factors at play in Kerala and Uttarakhand. There have been two rainy “low pressure systems” that have been active in the Arabian Sea as well as the Bay of Bengal since last week. The Arabian Sea low pressure system contributed to the heavy rains in Kerala, while the western disturbances, which are periodic inflows of moisture-laden clouds from the Mediterranean, and common during winter , are the source of the rains in northern India. The Bay of Bengal is still warm and the resulting strong winds reach Uttarakhand and will contribute to precipitation in several parts of northeast India.
October is the month when the southwest monsoon completely withdraws from India and the northeast monsoon sets in, bringing rains to Tamil Nadu, Puducherry, the coast of Andhra Pradesh and Kerala. Low pressures as well as western disturbances are tangentially linked to the larger pattern of global warming. The Bay of Bengal is historically the warmest ocean that sows the low pressures and cyclones that bring rains to India. In recent years, however, the Arabian Sea has also been warmer than normal and resulted in significant cyclonic activity. Overall, the high temperatures also contribute to the warming of the waters of the Arctic Ocean and attract colder air from the poles with greater intensity. This added to the increase in humidity, sowing more intense western disturbance activity over northern India.
Is the delayed monsoon retreat responsible?
This year, the monsoon began its retreat on October 6, and while it is expected to recede completely by October 16, it has not yet fully receded, clouds persistent associates. The latest IMD estimate is that the monsoon will recede completely by October 26 and this will also herald the onset of the northeast monsoon. When the atmosphere and the ocean are taken as a whole, rain everywhere is a result of moisture rushing to bridge the temperature differences between the oceans and the land and although there is a broad consensus on the As warming oceans contribute to intense episodes of rain in the pockets followed by long periods without rain, specific cases – such as what is seen in Kerala and Uttarakhand – are not without precedent. The monsoon cycle is subject to great variations, and each year regional factors are accentuated – it is difficult to predict which ones in advance – which then leads to extreme weather events.
What are the factors responsible for disasters?
This year India was on the verge of receiving below normal rainfall until August, when global weather factors changed and produced a torrential September which largely made up for the monsoon deficit. However, climatic hazards reveal their impact in the damage they cause and the damage is due to the environmental choices of society. Kerala and Uttarakhand have large tracts of hilly land prone to landslides. But construction continued unabated, even on land unsuitable for human habitation. Several ecologists and environmentalists have for years warned of the consequences of unplanned development and, against the backdrop of an increasingly erratic climate, it makes sense that more people in these regions are exposed to a greater climate risk.